John Crane Gas Seals

Gas seals and their application for maximum reliability

John Crane Turbomachinery

Products & Operation

DGS Application Range

John Crane DGS

Operating Range

Temp: -140 to +315°C Pressure: to 450 Barg Speed: to 200m/s Shaft: to 330mm

Type 28AT Seal Design Features

Compliant stationary face design providing

• maximum flexibility

• Optimum slow roll capability

Logarithmic spiral or bi-directional design.

Tungsten carbide or silicon carbide rotating seat

Type 28 AT for duties to 82 bar

Carbon seal faces

Elastomeric ‘O’ Ring

Secondary seal

Type 28 XP for duties to 200 bar

Keyed Balance dia. polymer

Carbon seal faces

Type 28 EXP for duties to 350 bar

Cranite seal faces

ADC Balance dia. polymer

John Crane T28 Gas Seal

Standard Application Envelope

0

50

100

150

200

250

300

350

50 100 150 200 250 300

Shaft Diameter (mm)

Max

Pre

ssu

re (

bar

g)

- S

tati

c o

r D

ynam

ic

John CraneRange of Standard gas seals

High Speed

Re-injection Duties

LNG type Duties

Type 28 XPType 28 XP

Type 28 EXPType 28 EXP

John Crane dominate High Technology Market sectorsJohn Crane dominate High Technology Market sectorsType 28 AT Type 28 AT

Core business

Type 82 Barrier seal

Benefits Proven / reliable design

>15 years field experience on a wide range of applications

Excellent protection against Oil ingress into DGS

limited N2 Consumption

No explosive mixture risk

No process gas to bearing housing

Environmentally Friendly

Control Panels & SEPro Systems

Complex Gas Seal control panel & booster for BP Horn Mountain

SEPro system for BP

0

50

100

150

200

250

300

350

400

450

1985 1990 1995 2000 2005

Pre

ssur

e (B

ar)

Gas seal performance progress

AT Triple

AT TripleXP Tandem

XP Tandem

XP Triple

XP Triple

XP Quad

XP Quad

EXP Tan

dem

EXP Tan

dem

(Cra

nite &

(Cra

nite &

ADC)

ADC)

AT Tandem

AT Tandem

John Crane Turbomachinery

Seal design for maximum reliability

John Crane Turbomachinery

System design for maximum reliability

80% of seals fail prematurely because of contamination

Ensure the gas is clean and dry

Process Gas

FI FI

FILTER MODULE

PROCESSGAS

EXTERNALGAS

Filtered Process Gas For extended reliability

clean / dry seal gas is the MOST important• Gas should be filtered

to around 1 micron• Coalescing filters can

be used to dry the gas• Heaters can be used to

provide superheat• Heat tracing should be

used to prevent heat loss

• SEPro type systems can be used to provide static gas flow

AF 15256 Gas Composition

0

20

40

60

80

100

120

140

160

180

-180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60

Temperature (C)

Pre

ssur

e (b

ar)

dew line bubble line Adiabatic Expansion Hydrate Curve (1% H2O)

Phase Diagrams

Check adiabatic expansion Check hydrate formation

Using a thermocouple to measure seal temp

•End User in Alaska•5.687” Seal on Suction End•6.929” seal On Discharge•Reinjection duty with H2S

•325 bar working pressure•350 bar max pressure •11753 rpm•Operating since August 2000

Specify a Thermocouple to

monitor seal temp

OEM will need to provide

exit gland

AF 15254-59°C Dew Point

0

20

40

60

80

100

120

140

160

180

-200 -150 -100 -50 0 50 100 150

Temperature (C)

Pre

ss

ure

(b

ar)

dew line bubble line Adiabatic Expansion Hydrate Curve

Gas from Skid Seal Gas DE Seal Gas NDE

Field Gas Analysis - Plot operating conditions

AF 15254-59°C Dew Point

0

20

40

60

80

100

120

140

160

180

-200 -150 -100 -50 0 50 100 150

Temperature (C)

Pre

ss

ure

(b

ar)

dew line bubble line Adiabatic Expansion Hydrate Curve

Gas from Skid Seal Gas DE Seal Gas NDE

Field Gas Analysis - Plot operating conditions

Measured operating points from Data capture system

Predicted worst case expansion line

Actual worst case expansion line passing through liquid region

Review gas properties

White deposits found across IB seal faces

Caused seat and face to stick together

Clear evidence of liquid contamination

Area analysed

Element Wt%

C K 09.62

O K 09.40

AlK 00.11

SiK 00.32

S K 80.55

White deposits identified as deposition of elemental sulphur

John Crane Turbomachinery

- Create a clean environment for the seal under all conditions

Clean seal gas injection – Normal operation

Process Gas

FI FI

FILTER MODULE

PROCESSGAS

EXTERNALGAS

Filtered Process GasFlow path of seal gas under normal dynamic operating conditions

FI FI

Filter No differential pressure= no flow

Seal contaminated by process gas

Can Lead to Seal hang up on start-up

No seal gas flow at settle out conditions

Settle- out Conditions (Pressurised standstill)

SEPro - Superior by design

• Application developed gas circulator

• Inbuilt safety and monitoring features

• Plug and play operating philosophy

• Auto start / stop functions

• Onboard logic and control

SEPro - Heated filtered seal gas on demand duringshutdown and periods of low differential pressureensure the seal is constantly maintained in optimumcondition and readiness for re-start.

Seal environment solutions Seal environment solutions fromfrom

When the unit is statically pressurised

there is no seal gas flow

JT expansion causes cooling

Any liquids or heavy ends are deposited in

the seal

This results in serious contamination and

premature seal failure

The SEPro system provides flow to keep

the seals clean and dry

Provides major increase in seal life

Seal environment solutions Seal environment solutions fromfrom

HEATERMODULE

PI

FIT

N2 PURGE

VENT

VENT

TE

PI

VENT

PI

GAS BOOSTER

CONTROLMODULE

PI PI

MONITORING OUTPUTS

AIRSUPPLY

STATUSPANEL

S

FROM MAIN SEAL GAS FILTERS FEED TO DRY GAS SEALS

FILTER

NC

NC

NC

NC

SEPro Flow diagram

Seal environment solutions Seal environment solutions fromfrom

SEPro - More than just another filtered gas package

Maintain optimum seal condition

Increase compressor availability

Prevent liquid contamination at seal faces

Prevent process debris contamination

Increase dry gas seal MTBF

NACE material compatibility

ATEX and PED options

Experience has proven that process contamination is the biggest single contributor to premature gas seal failure

John Crane Turbomachinery

Ensure the OB seal is adequately alarmed

Ensure the OB seal is adequately alarmed

FI FI

N2 SECONDARYFILTER MODULE

PCV

Filtered N2 Secondary Gas

FLAREFI

PI

FO

PI

FO

FI

Process Gas

FI FI

FILTER MODULE

PROCESSGAS

EXTERNALGAS

Filtered Process Gas

Process + N2

Gas to Flare

Ensure OB seal is alarmed• LP in PV = OB seal failure

• HP in PV = IB seal failure

John Crane Turbomachinery

Ensure adequate separation from bearing oil

Type 82 Barrier Seal - Function

VENT

N2 to Atmosphere

Ensure adequate Barrier Seal Supply

FI FI

N2 SECONDARYFILTER MODULE

PCV

Filtered N2 Secondary Gas

FLAREFI

PI

FO

PI

FO

FI

Process Gas

FI FI

FILTER MODULE

PROCESSGAS

EXTERNALGAS

Filtered Process Gas

Process + N2

Gas to Flare

Ensure Barrier gas supply pressure is adequately controlled• Should be controlled

to 0.3 to 0.5 bar• Barrier Seal leakage

changes with time

• Interlock with bearing oil

PI PI

Barrier seal pressure controlled with PCV’s

Type 82 Bushing Upgrade - the Type 83 Barrier Seal

Improved Product - Type 83 Barrier Seal

Carbon Segments

Garter Spring

Wave Spring

Type 83 Barrier Seal

New Development - Type 83 Barrier Seal

Oil side

Dry Gas Seal side

Type 83 Barrier Seal

John Crane Turbomachinery

Ensure The OEM’s test with job seal system

Ensure the compressor is tested with job panel

Complex Gas Seal control panel & booster for BP Horn Mountain

The OEM’s often provide a

temporary seal system for the

compressor testing.

• Complex systems are left untested

• SD conditions left unchecked

• Lead to ‘prototype’ trials on site

If there is a problem with the seal it is

often not picked up

• Catastrophic failure

• Impossible to diagnose

Specification for maximum reliability- Summary

Use polymer seals in place of O rings• Even at low pressures XP seal show benefits

Ensure the gas is clean and dry• Use coalescing filters to remove liquids

• Ensure adequate draining

• Heat trace lines + insulate

• Use SEPro system to provide seal gas under shutdown

• Protects the seal from process gas when the machine is shutdown

• Use heaters to increase margin over liquid formation

• Use a thermocouple within the seal to monitor temp

Ensure adequate OB seal failure sensing Confirm test conditions reflect duty

• Axial movements• Transient movement Vacuum testing

• Temperature transients• Confirm seal vendor test conditions reflect duty

Leakage monitoring• Ensure flowmetres are correctly sized• Check shutdown flow rates

Barrier seal gas system• Ensure adequate barrier seals are provided• Adequate pressure control (0.3 to 0.5 bar)• Confirm failure sensing• Provide bearing oil interlock• Consider explosive mixtures / including failure condition

Specification for maximum reliability- Summary

John Crane Gas Seals Offer:-

Experience• More experience than the other gas seal vendors put

together

Global service• Local experience and support• Local repair service• All to a guaranteed global standard

Technology• Proven high performance products specially selected for

specific requirements

John Crane – World leaders in Dry Gas Seal Technology